Organic light emitting diode display device and method of manufacturing the same

ABSTRACT

An OLED display device includes a plurality of pixels including sub-pixels arranged along a first direction, the sub-pixels being arranged in an order emitting red, green, and blue lights along the first direction or in a reverse order, wherein an arrangement of colors of light emitted from sub-pixels of one pixel is symmetrical to an arrangement of colors of light emitted from sub-pixels of an adjacent pixel, and wherein a light emitting layer of the sub-pixel emitting red light includes a light emitting layer emitting red light and a light emitting layer emitting green light, a light emitting layer of the sub-pixel emitting green light includes a light emitting layer emitting green light, and a light emitting layer of the sub-pixel emitting blue light includes a light emitting layer emitting blue light and a light emitting layer emitting green light.

BACKGROUND

1. Field

Example embodiments relate to an organic light emitting diode displaydevice. More particularly, example embodiments relate to a highresolution organic light emitting diode display device, whereindeposition of a light emitting layer for each sub-pixel is easy andprecision of patterns of sub-pixels is improved.

2. Description of the Related Art

As organic light emitting diode (OLED) display devices have a wideviewing angle, excellent contrast ratio, and high response speed, theyare considered as the next-generation display devices.

An OLED display device may include a first electrode and a secondelectrode facing each other, and an intermediate layer including atleast a light emitting layer between the first and second electrodes.The first electrode, the second electrode, and the intermediate layermay be formed using various methods, such as a deposition method. Whenthe deposition method is used, a mask with opening portions having thesame patterns as the patterns of a film to be deposited is used. Themask may be closely adhered to a surface where the film is to be formed,and a material may be deposited on the surface through the mask to forma thin film having predetermined patterns.

When the conventional OLED display device includes a plurality ofpixels, e.g., each pixel including red, green and blue sub-pixels, lightemitting layers of the sub-pixels may be formed using the depositionmethod. For example, the light emitting layers of all the sub-pixelsemitting red light may be formed by deposition through a mask at thesame time, and then the light emitting layers of all the sub-pixelsemitting blue light may be formed by deposition at the same time, andthen the light emitting layers of all the sub-pixels emitting greenlight may be formed by deposition at the same time.

However, since distances between adjacent sub-pixels become smaller inorder to manufacture display devices having high image quality, thedistance between the opening portions of a mask for depositing lightemitting layers of sub-pixels may be also reduced. For example, if red,green, and blue sub-pixels are repeatedly formed in this order along afirst direction, a distance along the first direction between twoadjacent opening portions of the mask for the blue light emitting layerin QCIF OLED having a resolution of 140 ppi may be about 0.068 mm, i.e.,a distance along the first direction between two adjacent sub-pixelsemitting blue light. While a conventional fine pitch mask, e.g., a maskin which the distance between adjacent opening portions is about 0.068mm, may facilitate manufacturing of an OLED display device having highimage quality, there may be many limitations, e.g., physical limits, inmanufacturing such a fine pitch mask. In addition, as the pitch of themask is reduced, it may be difficult to pattern a mask and to align thepatterns of the mask with corresponding portions of the OLED displaydevice, i.e., portions where the light emitting layers are to bedeposited. Inaccurate alignment and patterning of the mask may causeinaccurate film deposition of the light emitting layers, therebyreducing display properties and image quality of the OLED displaydevice.

SUMMARY

Example embodiments are therefore directed to an OLED display device anda method of manufacturing the same, which substantially overcome one ormore of the problems due to the limitations and disadvantages of therelated art.

It is therefore a feature of an example embodiment to provide an OLEDdisplay device having an arrangement of sub-pixels that providesimproved deposition with an increased precision.

It is therefore another feature of an example embodiment to provide amethod of manufacturing an OLED display device by arranging sub-pixelstherein to provide improved deposition and precision.

At least one of the above and other features and advantages may berealized by providing an OLED display device, including a plurality ofpixels, wherein each of the pixels comprises sub-pixels respectivelyemitting red, blue, and green light in the order or reverse order alonga first direction, wherein the sub-pixels formed in the pixels along thefirst direction of the organic light emitting display device aredisposed such that the arrangement of colors of light emitted from eachsub-pixel of one pixel is symmetrical to the arrangement of colors oflight emitted from each sub-pixel of the neighboring pixel with respectto a space between the pixels along the first direction, and wherein alight emitting layer of the sub-pixel emitting red light comprises alight emitting layer emitting red light and a light emitting layeremitting green light, and a light emitting layer of the sub-pixelemitting the green light comprises a light emitting layer emitting greenlight, and a light emitting layer of the sub-pixel emitting blue lightcomprises a light emitting layer emitting blue light and a lightemitting layer emitting green light.

Each of the sub-pixels may include a first electrode and a secondelectrode facing each other, and the light emitting layer of each of thesub-pixels is interposed between the first electrode and the secondelectrode, and wherein the light emitting layer emitting red light orthe light emitting layer emitting blue light of two sub-pixels adjacentto each other with respect to a space between the adjacent pixels alongthe first direction is formed as one unit.

The light emitting layer emitting green light of the plurality of thesub-pixels may be formed as one unit.

Each of the sub-pixels may include an anode electrode and a cathodeelectrode facing each other, and a light emitting layer of each of thesub-pixels is interposed between the anode electrode and the cathodeelectrode, and a light emitting layer emitting red light of thesub-pixel emitting red light may be disposed between a light emittinglayer emitting green light of the sub-pixel emitting red light and theanode electrode, and a light emitting layer emitting blue light of thesub-pixel emitting blue light may be disposed between a light emittinglayer emitting green light of the sub-pixel emitting blue light and theanode electrode.

The hole mobility of the light emitting layer emitting red light of thesub-pixel emitting red light may be lower than the hole mobility of thelight emitting layer emitting green light, and the electron mobility ofthe light emitting layer emitting green light may be higher than theelectron mobility of the light emitting layer emitting red light.

The hole mobility of the light emitting layer emitting blue light of thesub-pixel emitting blue light may be lower than the hole mobility of thelight emitting layer emitting green light, and the electron mobility ofthe light emitting layer emitting green light may be higher than theelectron mobility of the light emitting layer emitting blue light.

Each of the sub-pixels may include an anode electrode and a cathodeelectrode facing each other, and a light emitting layer of each of thesub-pixels is interposed between the anode electrode and the cathodeelectrode, and a light emitting layer emitting green light of thesub-pixel emitting red light may be disposed between a light emittinglayer emitting red light of the sub-pixel emitting red light and theanode electrode, and a light emitting layer emitting green light of thesub-pixel emitting blue light may be disposed between a light emittinglayer emitting blue light of the sub-pixel emitting blue light and theanode electrode.

The electron mobility of the light emitting layer emitting red light ofthe sub-pixel emitting red light may be lower than the electron mobilityof the light emitting layer emitting green light, and the hole mobilityof the light emitting layer emitting green light may be higher than thehole mobility of the light emitting layer emitting red light.

The electron mobility of the light emitting layer emitting blue light ofthe sub-pixel emitting blue light may be lower than the electronmobility of the light emitting layer emitting green light, and the holemobility of the light emitting layer emitting green light may be higherthan the hole mobility of the light emitting layer emitting blue light.

The sub-pixels in a second direction that is perpendicular to the firstdirection may emit light of the same color.

Each of the sub-pixels may include a first electrode and a secondelectrode facing each other, and a light emitting layer of each of thesub-pixels may be interposed between the first electrode and the secondelectrode, and the light emitting layers emitting red light or bluelight of two of the sub-pixels adjacent to each other with respect to aspace between the adjacent pixels along the first direction may beformed as one unit.

The light emitting layers of the sub-pixels in the second direction maybe formed as one unit. The sub-pixels arrangement along the firstdirection with respect to color of light emitted from respectivesub-pixels may include an order of red, green, blue, blue, green, red,red, green, blue, blue, and so forth.

At least one of the above and other features and advantages may berealized by providing a method of forming an OLED display device,including forming a plurality of pixels including sub-pixels in apredetermined order along a first direction, each sub-pixel emittingred, green, or blue light, and the predetermined order of the sub-pixelsincluding sub-pixels arranged in an order emitting red, green, and bluelights along the first direction or in a reverse order, wherein thesub-pixels formed in the pixels along the first direction are disposed,such that the arrangement of colors of light emitted from sub-pixels ofone pixel is symmetrical to an arrangement of colors of light emittedfrom sub-pixels of an adjacent pixel along the first direction, an axisof symmetry of the symmetrical arrangement being a space between theadjacent pixels, and wherein a light emitting layer of the sub-pixelemitting red light is formed to include a light emitting layer emittingred light and a light emitting layer emitting green light, a lightemitting layer of the sub-pixel emitting green light is formed toinclude a light emitting layer emitting green light, and a lightemitting layer of the sub-pixel emitting blue light is formed to includea light emitting layer emitting green light and a light emitting layeremitting blue light.

Forming each sub-pixel may include forming the light emitting layerbetween a first electrode and a second electrode, light emitting layersemitting red light or light emitting layers emitting blue light of twoadjacent sub-pixels of respective pixels adjacent to each other alongthe first direction being formed as one unit via a single opening in adeposition mask. A light emitting layer emitting green light may beformed as one unit. The sub-pixels in a second direction may be arrangedto emit light of a same color, the second direction being perpendicularto the first direction. The light emitting layers of the sub-pixels inthe second direction may be formed as one unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more apparent tothose of ordinary skill in the art by describing in detail exemplaryembodiments with reference to the attached drawings, in which:

FIG. 1 illustrates a plan view of patterns of light emitting layers of aconventional OLED display device;

FIG. 2 illustrates a plan view of a conventional mask for depositingblue light emitting layers of the OLED display device of FIG. 1;

FIG. 3 illustrates a plan view of patterns of light emitting layers ofan OLED display device according to an example embodiment;

FIG. 4 illustrates a cross-sectional view of a plurality of sub-pixelsof the OLED of FIG. 3;

FIG. 5 illustrates a plan view of a mask for depositing blue lightemitting layers of the OLED display device of FIG. 3;

FIG. 6 illustrates a plan view of another example embodiment of a maskfor depositing green light emitting layers of the OLED display device ofFIG. 3; and

FIG. 7 illustrates a cross-sectional view of a plurality of sub-pixelsof an OLED display device according to another example embodiment.

DETAILED DESCRIPTION

Korean Patent Application No. 10-2008-0054858, filed on Jun. 11, 2008 inthe Korean Intellectual Property Office, and entitled “Organic LightEmitting Display”, is incorporated by reference herein in its entirety.

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. It will also be understood thatwhen a layer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. Further, it will be understoodthat when a layer is referred to as being “under” another layer, it canbe directly under, and one or more intervening layers may also bepresent. In addition, it will also be understood that when a layer isreferred to as being “between” two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent. Like reference numerals refer to like elements throughout.

FIG. 3 illustrates a plan view of a schematic arrangement of lightemitting layers of an OLED display device 100 according to an exampleembodiment, and FIG. 4 illustrates a cross-sectional view of a pluralityof sub-pixels of the OLED display device 100 of FIG. 3. FIG. 3illustrates the patterns of light emitting layers of the OLED displaydevice 100, and it may also be regarded as illustrating each ofsub-pixels for convenience of understanding. The same applies also toembodiments to be described later.

Referring to FIG. 3, the OLED display device 100 may include a pluralityof pixels 110, 120, 130, and 140. Each of the pixels may include asub-pixel emitting red light, a sub-pixel emitting green light, and asub-pixel emitting blue light along a first direction, e.g., along anx-direction in FIG. 3. The plurality of pixels may respectively includea plurality of corresponding sub-pixels emitting red light, green light,and blue light in this order or in a reverse order along the firstdirection. The sub-pixels included in the pixels along the firstdirection (x-direction) of the OLED display device 100 may be disposedso that an arrangement of sub-pixels in each pixel may be symmetrical toan arrangement of sub-pixels in an adjacent pixel with respect to aspace between the two adjacent pixels along the first direction.

For example, the pixels 110, 120, 130, and 140 may be arranged in a rowalong the first direction, i.e., the x-direction of FIG. 3, and mayinclude sub-pixels emitting red, green, and blue light along thex-direction. Assuming that the pixels disposed in the uppermost row ofthe patterns of the light emitting layers (sub-pixels) illustrated inFIG. 3 are each a first pixel 110, a second pixel 120, a third pixel130, and a fourth pixel 140, the first pixel 110 may include a sub-pixel110R emitting red light, a sub-pixel 110G emitting green light, and asub-pixel 110B emitting blue light along the x-direction.

Similarly, the second pixel 120, the third pixel 130, and the fourthpixel 140 may include sub-pixels. The sub-pixels 120R, 120G, and 120B ofthe second pixel 120 adjacent to the first pixel 110 may be arranged tobe symmetrical to the sub-pixels 110R, 110G, and 110B of the first pixel110 with respect to a space between the first pixel 110 and the secondpixel 120. In other words, the sub-pixels 120R, 120G, and 120B of thesecond pixel 120 that respectively emit red light, green light, and bluelight may be arranged to be symmetrical to the arrangement of thesub-pixels 110R, 110G, and 110B of the first pixel 110 respectivelyemitting red light, green light, and blue light with respect to thespace between the first pixel 110 and the second pixel 120. Accordingly,as illustrated in FIG. 3, when the first pixel 110 includes thesub-pixel 110R emitting red light, the sub-pixel 110G emitting greenlight, and the sub-pixel 110B emitting blue light along the x-direction,the second pixel 120, which is adjacent to the first pixel 110, mayinclude the sub-pixel 120B emitting blue light, the sub-pixel 120Gemitting green light, and the sub-pixel 120R emitting red light alongthe x-direction. In other words, as illustrated in FIG. 3, thesub-pixels of the first and second pixels 110 and 120 may be arranged sothe blue light emitting sub-pixels 110B and 120B of the first and secondpixels 110 and 120, respectively, may be adjacent to each other.

Also, the sub-pixels 130R, 130G, and 130B of the third pixel 130emitting red light, green light, and blue light, respectively, may bearranged to be symmetrical to the arrangement of the sub-pixels 120R,120G, and 120B of the second pixel 120 with respect to a space betweenthe second pixel 120 and the third pixel 130. Accordingly, asillustrated in FIG. 3, as the second pixel 120 includes the sub-pixel120B emitting blue light, the sub-pixel 120G emitting green light, andthe sub-pixel 120R emitting red light along the x-direction, the thirdpixel 130, which is adjacent to the second pixel 120, may include thesub-pixel 130R emitting red light, the sub-pixel 130G emitting greenlight, and the sub-pixel 130B emitting blue light along the x-direction.In other words, as illustrated in FIG. 3, the sub-pixels of the secondand third pixels 120 and 130 may be arranged so the red light emittingsub-pixels 120R and 130R of the second and third pixels 120 and 130,respectively, may be adjacent to each other.

The fourth pixel 140 and other pixels may include sub-pixels arranged inthis manner, and consequently, the sub-pixels R emitting red light, thesub-pixels G emitting green light, and the sub-pixels B emitting bluelight of the OLED display device 100 may be arranged in the order of R,G, B, B, G, R, R, G, B, B, G, R, etc. along the first direction, asillustrated in FIG. 3. For example, as further illustrated in FIG. 3,the sub-pixels in the OLED display device 100 along the y-direction maybe arranged so each column of sub-pixels along the y-direction has asame color.

The configuration of the OLED display device 100 according to thecurrent embodiment of the present invention will be described withreference to FIG. 4, which is a cross-sectional view illustrating aplurality of sub-pixels of the OLED display device 100 having thearrangement described previously with reference to FIG. 3.

FIG. 4 illustrated a schematic view of a portion of the first pixel 110,the second pixel 120, and the third pixel 130.

Referring to FIG. 4, a plurality of thin film transistors 220 may beformed on a substrate 200, and organic light emitting elements 230B,230G, and 230R may be formed on the thin film transistors 220. Each ofthe organic light emitting elements 230B, 230G, and 230R may include afirst electrode 231 electrically connected to a respective thin filmtransistor 220, a second electrode 235 disposed over the entire surfaceof the substrate 200, and a light emitting layer disposed between thefirst electrode 231 and the second electrode 235.

The thin film transistors 220 may be formed on the substrate 200, andmay include a gate electrode 221, a source electrode and a drainelectrode 223, a semiconductor layer 227, a gate insulating layer 213,and an interlayer insulating layer 215. However, the thin filmtransistor 220 is not limited to the embodiment illustrated in FIG. 4,and various thin film transistors, e.g., an organic thin film transistorincluding an organic semiconductor layer, a silicon thin film transistorformed of silicon, and so forth may be used. A buffer layer 211, e.g.,formed of silicon oxide or silicon nitride, may be further includedbetween the thin film transistor 220 and the substrate 200.

The organic light emitting elements 230B, 230G, and 230R may include thefirst electrode 231, the second electrode 235, and a light emittinglayer interposed therebetween and formed of an organic material.

The first electrode 231 may function as an anode electrode, and thesecond electrode 235 may function as a cathode electrode. However, thepolarity of the first and second electrodes 231 and 235 may be changed.

The first electrode 231 may be formed as a transparent electrode or areflective electrode. When formed as a transparent electrode, the firstelectrode 231 may be formed of, e.g., one or more of indium tin oxide(ITO), indium zinc oxide (IZO), ZnO, and In₂O₃. When formed as areflective electrode, the first electrode 231 may include a reflectionlayer formed of, e.g., one or more of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd,Ir, Cr or compound of any of these, and a transparent layer, e.g.,formed of one or more of ITO, IZO, ZnO, and In₂O₃, may be formed on thereflection layer.

The second electrode 235 may also be formed as a transparent electrodeor a reflective electrode. When formed as a transparent electrode, thesecond electrode 235 may include a layer of Li, Ca, LiF/Ca, LiF/Al, Al,Mg, or a compound of any of these deposited on the light emitting layer,and may also include a bus electrode line or an auxiliary electrodeformed of a material for a transparent electrode, e.g., ITO, IZO, ZnO,or In₂O₃. When formed as a reflective electrode, the second electrode235 may be formed by depositing, e.g., Li, Ca, LiF/Ca, LiF/Al, Al, Mg,or a compound of any of these.

Also, a pixel defining layer (PDL) 219 may be formed to cover an edge ofthe first electrode 231 and to have a predetermined thickness away fromthe first electrode 231. Besides the function of defining a lightemitting region at the edge portion of the PDL 219, the second electrode235 may be spaced apart from the first electrode 231 by a distancecorresponding to the thickness of the PDL 219 located therebetween.Accordingly, concentration of an electric field at the edge portion ofthe first electrode 231 may be prevented, thereby preventing a shortcircuit between the first electrode 231 and the second electrode 235.

A light emitting layer may be interposed between the first and secondelectrodes 231 and 235. The light emitting layer will be described inmore detail below.

The organic light emitting elements 230B, 230G, and 230R may beelectrically connected to the thin film transistor 220 therebelow, and aplanarizing layer 217 may be formed between the thin film transistors220 and the organic light emitting elements 230B, 230G, and 230R. Theplanarizing layer 217 may be formed to cover and protect the thin filmtransistors 220, and the organic light emitting elements 230B, 230G, and230R may be disposed on the planarizing layer 217, so the firstelectrodes 231 of the organic light emitting elements 230B, 230G, and230R may be electrically connected to respective thin film transistors220 via contact holes through the planarizing layer 217.

The organic light emitting elements 230B, 230G, and 230R may beencapsulated by a counter substrate 300. The counter substrate 300 maybe formed of various materials, e.g., glass or plastics.

As described above, the sub-pixels included in the pixels of the OLEDdisplay device 100 along the first direction (x-direction) may bedisposed such that the arrangement of the color of light emitted by eachof the sub-pixels of one pixel is symmetrical to the arrangement of thecolor of light emitted by each of the sub-pixels of the neighboringpixels adjacent along the first direction. That is, the sub-pixel 120Bemitting blue light may be disposed as a sub-pixel of the second pixel120 that may be adjacent to the sub-pixel 110B of the first pixel 110emitting blue light along the x-direction, and then the sub-pixel 120Gemitting green light and the sub-pixel 120R emitting red light of thesecond pixel 120 may be sequentially disposed after the sub-pixel 120B.Then the sub-pixel 130R of the third pixel 130 emitting red light may bedisposed adjacent to the sub-pixel 120R of the second pixel 120 emittingred light.

With respect to the arrangement of the sub-pixels, light emitting layersof the sub-pixels 120R and 130R emitting red light may include a lightemitting layer 233R emitting red light and a light emitting layer 233Gemitting green light. A light emitting layer of the sub-pixel 120Bemitting blue light may include a light emitting layer 233B emittingblue light and a light emitting layer 233G emitting green light. A lightemitting layer of the sub-pixel 120G emitting green light may include,e.g., only, a light emitting layer 233G emitting green light.

For example, when forming light emitting layers of the OLED displaydevice 100, i.e., having sub-pixels arranged as described above, bluelight emitting layers may be deposited with a mask 100Bm illustrated inFIG. 5. The mask 100Bm may include opening portions 110Bm, 120Bm, 130Bm,and 140Bm, as illustrated in FIG. 5. Reference numerals 110Bm and 120Bmdenote the same opening portions and reference numerals 130Bm and 140Bmdenote the same opening portions. For example, opening portions 110Bmand 120Bm may correspond to the light emitting layer 233B of thesub-pixel 110B of the first pixel 110 emitting blue light and the lightemitting layer 233B of the sub-pixel 120B of the second pixel 120emitting blue light, respectively. Similarly, opening portions 130Bm and140Bm may correspond to the blue light emitting layers of the third andfourth pixels 130 and 140 that are adjacent to each other. That is, byusing the mask 100Bm having opening portions having patterns asillustrated in FIG. 5, the light emitting layers 233B emitting bluelight of the sub-pixels 110B and 120B adjacent to each other may beformed as one unit, and the blue light emitting layers of the third andfourth pixels 130 and 140 adjacent to each other may be formed as oneunit. A distance l1 refers to a distance along the first directionbetween adjacent blue patterns, i.e., opening portions, in the mask100Bm. It is noted that a similar mask (not illustrated) may be used fordepositing the light emitting layers 233R emitting red light of, e.g.,the sub-pixels 120R and 130R, adjacent to each other as one unit.

Since the light emitting layer 233G emitting green light may be formedover the entire surface of the substrate 200 as illustrated in FIG. 4,the light emitting layer 233G emitting green light may be formed bydeposition using a general open mask. That is, the light emitting layers233G emitting green light may be formed as one unit with respect to aplurality of the sub-pixels, e.g., the light emitting layers 233Gemitting green light may be formed in all the sub-pixels of the OLEDdisplay device 100. In the case of the OLED display device 100illustrated in FIG. 4, light emitting layers 233B emitting blue lightand light emitting layers 233R emitting red light may be formed on thefirst electrodes 231, and then light emitting layers 233G emitting greenlight may be formed over the entire surface of the substrate 200.

As described above, referring to FIG. 5 illustrating the mask 100Bmhaving patterned opening portions used in manufacturing light emittinglayers of the OLED display device 100 according to example embodiments,as the size of the opening portions included in the mask 100Bm isincreased relative to a conventional mask, e.g., to correspond to twoadjacent sub-pixels, a distances l1 between the opening portions may bealso increased, e.g., to overlap about four sub-pixels between theopening portions. Accordingly, as the size of the sub-pixels and adistance therebetween is decreased, a decrease in a size of the openingportions in the mask 100Bm and the distances l1 therebetween may besmall relative to an initial size thereof. In other words, since theopening portions included in the mask 100Bm and distances therebetweenare at least twice as large as sizes of openings and distancestherebetween in a conventional mask, a decreased size of sub-pixels mayhave a smaller effect on a pitch of the mask 100Bm as compared toconventional masks, thereby facilitating accurate patterning andalignment.

In particular, when sub-pixels 11 to 14 of a conventional OLED displaydevice 10 are arranged repeatedly along the first direction, e.g., eachpixel including sub-pixels R, G, B, etc. in that order, as illustratedin FIG. 1, a conventional mask for depositing corresponding lightemitting layers may have a separate opening portion for each sub-pixel.For example, as illustrated in FIG. 2, each opening portion in aconventional mask 10Bm, i.e., each of openings 11Bm through 14Bm, maycorrespond to a blue light emitting layer of a single sub-pixel emittingblue light. As further illustrated in FIG. 2, for example, openingportions 11Bm and 12Bm corresponding to sub-pixels emitting blue lightmay have a distance l0 therebetween, i.e., a distance overlapping abouttwo sub-pixels, so a decreased size of the sub-pixels may cause areduced distance l0 therebetween, e.g., below about 0.068 mm. Sincethere are physical limits to a reduced pitch of the conventional mask10Bm in FIG. 2, formation of the conventional OLED display device 10 viathe conventional mask 10Bm may include inaccurate sub-pixel deposition.

However, the sub-pixel arrangement according example embodiments and useof the mask 100Bm illustrated in FIG. 5 may facilitate reduced sub-pixelsize, while maintaining ease of mask patterning and alignment, andproviding easy formation of the light emitting layers. That is, when themask 100Bm illustrated in FIG. 5 is used to deposit light emittinglayers according to the arrangement of the sub-pixels of the OLEDdisplay device 100 illustrated in FIGS. 3 and 4, the distance l1 betweenthe opening portions 120Bm and 130Bm included in the mask 100Bm may belarger than the distance l0, e.g., the distance l1 may equal about 2*l0.Accordingly, the surface area of the opening portions 120Bm and 130Bmincluded in the mask 100Bm may be also two times of the surface area ofthe respective opening portions 11Bm and 12Bm included in theconventional mask 10Bm. In the case of a QCIF OLED display device havingresolution of 140 ppi, the distance l1 between the opening portions120Bm and 130Bm illustrated in FIG. 5 may be about 0.1368 mm, which issubstantially greater than the distance l0, i.e., about 0.068 mm,between the opening portions 11Bm and 12Bm included in the conventionalmask 10Bm illustrated in FIG. 2. Accordingly, the distance between theopening portions in the mask 100Bm in FIG. 5 may be further easilyreduced, and as a result, the OLED display device 100 may have highimage quality.

In another example, the light emitting layers 233B emitting blue lightof the sub-pixels 110B and 120B emitting blue light and adjacent to eachother may not be formed as one unit (not illustrated). In this case, oneopening portion commonly denoted with reference numerals 110Bm and 120Bmmay be divided into two opening portions adjacent to each other, i.e.,an opening portion 110Bm and an opening portion 120Bm. However, in thiscase, since the sub-pixels 110B and 120B are adjacent to each other andemit light of the same color, even if a minor error is generated indepositing the light emitting layers of the adjacent sub-pixels having aspace therebetween, image realization of the whole OLED display devicemay not be affected because the sub-pixels emit the same color of light.Thus, as the distance between the sub-pixels is reduced, decrease in theyield may be prevented and the manufacturing costs may be reduced whenmanufacturing a display device having high image quality and fine pitch.

As illustrated in FIG. 3, the sub-pixels in a second direction(y-direction) at a right angle to the first direction (x-direction) mayemit light of the same color. In this case, as illustrated in FIG. 6, amask in which the opening portions may be also formed as one unit alongthe second direction (y-direction) may be used. Here, the light emittinglayers may be formed as one unit along the second direction(y-direction).

As described above, in the OLED display device 100 having the structureillustrated in FIGS. 3 and 4, the light emitting layers of the sub-pixel120B emitting blue light may include the light emitting layer 233Gemitting green light in addition to the light emitting layer 233Bemitting blue light. Also, the light emitting layers of the sub-pixel120R emitting red light may include the light emitting layer 233Gemitting green light in addition to the light emitting layer 233Remitting red light. Accordingly, light emission of the sub-pixel 120Bemitting blue light may be adjusted, so that light emission may begenerated mainly in the light emitting layer 233B emitting blue light.Similarly, light emission of the sub-pixel 120R emitting red light maybe adjusted, so that light emission may be generated mainly in the lightemitting layer 233R emitting red light. To this end, materials of thelight emitting layer 233B emitting blue light, the light emitting layer233R emitting red light, and the light emitting layer 233G emittinggreen light may be selected appropriately.

When the first electrode 231 is an anode electrode and the secondelectrode 235 is a cathode electrode in the OLED display device 100 ofFIG. 4, holes may be supplied from the first electrode 231, andelectrons may be supplied from the second electrode 235. Meanwhile, thelight emitting layers 233R emitting red light of the sub-pixels 120R and130R emitting red light may be disposed adjacent to each other andbetween the light emitting layer 233G of the sub-pixels 120R and 130Remitting green light and the first electrode 231, i.e., the anodeelectrode. Accordingly, in order that light emission be mainly generatedin the light emitting layer 233R emitting red light of the sub-pixels120R and 130R emitting red light, material of the light emitting layer233R may be adjusted, so that holes supplied from the first electrode231 may remain in the light emitting layer 233R emitting red light andnot move to the light emitting layer 233G emitting green light. Thus,the hole mobility of the light emitting layer 233R emitting red light ofthe sub-pixels 120R and 130R emitting red light may be lower than thehole mobility of the light emitting layer 233G emitting green light.

For example, the light emitting layer 233R emitting red light may beformed of a material containing a methoxy electron donor side group, andthe light emitting layer 233G emitting green light may be formed of amaterial containing a dialkylamine(—NR2) electron donor side group.Further, in order that light emission is mainly generated in the lightemitting layer 233R emitting red light of the sub-pixels 120R and 130Remitting red light, materials of the light emitting layers may beselected so that electrons supplied from the second electrode 235 mayquickly pass through the light emitting layer 233G emitting green lightinto the light emitting layer 233R emitting red light to recombine withthe holes in the light emitting layer 233R. Accordingly, the electronmobility of the light emitting layer 233G emitting green light may behigher than the electron mobility of the light emitting layer 233Remitting red light. For example, the light emitting layer 233G emittinggreen light may be a material containing a cyano group (—CN) electronacceptor side group, and the light emitting layer 233R emitting redlight may be formed of a material containing a fluorine (—F) electronacceptor side group.

The above description is not limited to the sub-pixels 120R and 130Remitting red light, and may also be applied to the sub-pixels 110B and120B emitting blue light. In other words, regarding the OLED displaydevice 100 of FIG. 4, when the first electrode 231 is an anode electrodeand the second electrode 235 is a cathode electrode and the lightemitting layer 233B emitting blue light of the sub-pixels 110B and 120Bemitting blue light is disposed between the light emitting layer 233Gemitting green light and the first electrode 231, holes supplied fromthe first electrode 231 may preferably not move to the light emittinglayer 233G emitting green light, and the electrons supplied from thesecond electrode 235 may preferably quickly pass the light emittinglayer 233G emitting green light and arrive at the light emitting layer233B emitting blue light. Accordingly, the hole mobility of the lightemitting layer 233B emitting blue light of the sub-pixels 110B and 120Bemitting blue light may preferably be lower than the hole mobility ofthe light emitting layer 233G emitting green light.

For example, the light emitting layer 233B emitting blue light may beformed of a material containing a methoxy electron donor side group, andthe light emitting layer 233G emitting green light may be formed of amaterial containing a dialkylamine (—NR2) electron donor side group.Also, the electron mobility of the light emitting layer 233G emittinggreen light may preferably be higher than the electron mobility of thelight emitting layer 233B emitting blue light. Accordingly, e.g., thelight emitting layer 233G emitting green light may be a materialcontaining a cyano group (—CN) electron acceptor side group, and thelight emitting layer 233R emitting red light may be formed of a materialcontaining a fluorine (—F) electron acceptor side group.

FIG. 7 illustrates a cross-sectional view of a plurality of sub-pixelsof an OLED display device according to another embodiment of the presentinvention. The OLED display device of FIG. 7 is different from the OLEDdisplay device of FIG. 4 in terms of the structure of a light emittinglayer.

That is, in the case of the OLED display device described with referenceto FIG. 4, the light emitting layer 233B emitting blue light and thelight emitting layer 233R emitting red light may be deposited using themask illustrated in FIG. 5 or 6, and then the light emitting layer 233Gmay be deposited over the entire surface of the substrate 200, i.e., onthe deposited light emitting layer 233B emitting blue light and thelight emitting layer 233R emitting red light, using an open mask. In thecase of the OLED of FIG. 7, however, a light emitting layer 233Gemitting green light is deposited over the entire surface of thesubstrate 200 using an open mask, and then a light emitting layer 233Bemitting blue light and a light emitting layer 233R emitting red lightmay be deposited using a mask as illustrated in FIG. 5 or 6 on thedeposited light emitting layer 233G emitting green light. In the OLEDdisplay device illustrated in FIG. 7, a distance between the openingportions of the mask may be greater than that in the conventional OLEDdisplay device, and thus the distance between the opening portions maybe reduced easily when a size of sub-pixels is reduced, so an OLEDdisplay device having high image quality may be realized accordingly.

In the OLED display device of FIG. 7, a light emitting layer of thesub-pixel 110B emitting blue light may include a light emitting layer233G emitting green light in addition to the light emitting layer 233Bemitting blue light. Also, a light emitting layer of the sub-pixel 110Remitting red light may include a light emitting layer 233G emittinggreen light in addition to the light emitting layer 233R emitting redlight. Accordingly, light emission in the light emitting layer of thesub-pixel 110B emitting blue light may be adjusted, so that light may begenerated mainly in the light emitting layer 233B emitting blue light.Similarly, light emission in the light emitting layer of the sub-pixel110R emitting red light may be adjusted, so that light may be generatedmainly in the light emitting layer 233R emitting red light. To this end,materials of the light emitting layer 233R emitting red light, the lightemitting layer 233B emitting blue light, and the light emitting layer233G emitting green light may be selected appropriately.

In the OLED display device illustrated in FIG. 7, when the firstelectrode 231 is an anode electrode, and the second electrode 235 is acathode electrode, holes may be supplied from the first electrode 231,and electrons may be supplied from the second electrode 235. Meanwhile,the light emitting layer 233G emitting green light of the second andthird sub-pixels 120R and 130R emitting red light may be disposedbetween the light emitting layer 233R emitting red light of thesub-pixels 120R and 130R emitting red light and the first electrode 231,that is, the anode electrode. Accordingly, in order that light emissionbe mainly generated in the light emitting layer 233R emitting red lightof the sub-pixels 120R and 130R emitting red light, holes supplied fromthe first electrode 231 may preferably quickly pass through the lightemitting layer 233G emitting green light and arrive at the lightemitting layer 233R emitting red light. Accordingly, the hole mobilityof the light emitting layer 233G emitting green light of the sub-pixels120R and 130R may preferably be higher than the hole mobility of thelight emitting layer 233R emitting red light.

To this end, the light emitting layer 233G emitting green light may beformed of a material containing, e.g., a dialkylamine(—NR2) electrondonor side group, and the light emitting layer 233R emitting red lightmay be formed of a material containing, e.g., a methoxy electron donorside group. In order that light emission is mainly generated in thelight emitting layer 233R emitting red light of the sub-pixels 120R and130R emitting red light, electrons supplied from the second electrode235 may preferably not pass through the light emitting layer 233Remitting red light. Accordingly, the electron mobility of the lightemitting layer 233R emitting red light may preferably be higher than theelectron mobility of the light emitting layer 233G emitting green light.To this end, the light emitting layer 233R emitting red light may beformed of a material containing, e.g., a fluorine (—F) electron acceptorside group, and the light emitting layer 233G emitting green light maybe a material containing, e.g., a cyano group (—CN) electron acceptorside group.

The above description is not limited to the sub-pixels 120R and 130Remitting red light, and may also be applied to the sub-pixels 110B and120B emitting blue light. In other words, regarding the OLED displaydevice of FIG. 7, when the first electrode 231 is an anode electrode andthe second electrode 235 is a cathode electrode, and the light emittinglayer 233G emitting green light of the sub-pixels 110B and 120B emittingblue light is disposed between the light emitting layer 233B of thesub-pixels 110B and 120B emitting blue light and the first electrode231, which is an anode electrode, holes supplied from the firstelectrode 231 may preferably quickly pass through the light emittinglayer 233G emitting green light and arrive at the light emitting layer233B emitting blue light, and the electrons supplied from the secondelectrode 235 may preferably not pass the light emitting layer 233Bemitting blue light.

Accordingly, the hole mobility of the light emitting layer 233G emittinggreen light of the sub-pixels 110B and 120B emitting blue light maypreferably be higher than the hole mobility of the light emitting layer233B emitting blue light. To this end, the light emitting layer 233Gemitting green light may be formed of a material containing adialkylamine (—NR2) electron donor side group, and the light emittinglayer 233B emitting blue light may be formed of a material containing amethoxy electron donor side group.

Also, electron mobility of the light emitting layer 233B emitting bluelight may preferably be lower than the electron mobility of the lightemitting layer 233G emitting green light. To this end, the lightemitting layer 233R emitting red light may be formed of a materialcontaining a fluorine (—F) electron acceptor side group, and the lightemitting layer 233G emitting green light may be a material containing acyano group (—CN) electron acceptor side group.

As described above, according to example embodiments, an OLED displaydevice having high resolution may be manufactured, wherein lightemitting layers of each of the sub-pixels may be easily deposited, andpatterns of the sub-pixels may be manufactured with increased precision.

Although embodiments of the present invention including a structure inwhich a light emitting layer is interposed between the first electrode231 and the second electrode 235 have been described above, othervarious intermediate layers than a light emitting layer such as a holeinjection layer, a hole transport layer, an electron transport layer,and an electron injection layer may be inserted. The intermediate layermay be formed as one unit with the substrate over the entire surface ofthe substrate, or may be formed for each of pixels or for each ofsub-pixels, or may be formed as one unit with a plurality of the pixelsor with a plurality of the sub-pixels.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

Exemplary embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation.Accordingly, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made without departingfrom the spirit and scope of the present invention as set forth in thefollowing claims.

1. An organic light emitting diode (OLED) display device, comprising: aplurality of pixels including sub-pixels arranged in a predeterminedorder along a first direction, each sub-pixel emitting red, green, orblue light, and the predetermined order of the sub-pixels includingsub-pixels arranged in an order emitting red, green, and blue lightsalong the first direction or in a reverse order, wherein an arrangementof colors of light emitted from respective sub-pixels of one pixel issymmetrical to an arrangement of colors of light emitted from respectivesub-pixels of an adjacent pixel along the first direction, an axis ofsymmetry of the symmetrical arrangements being a space between theadjacent pixels, and wherein a light emitting layer of the sub-pixelemitting red light includes a light emitting layer emitting red lightand a light emitting layer emitting green light, a light emitting layerof the sub-pixel emitting the green light includes a light emittinglayer emitting green light, and a light emitting layer of the sub-pixelemitting blue light includes a light emitting layer emitting blue lightand a light emitting layer emitting green light.
 2. The OLED device asclaimed in claim 1, wherein each of the sub-pixels includes a firstelectrode and a second electrode facing each other, the light emittinglayer of each of the sub-pixels being interposed between the firstelectrode and the second electrode, and wherein the light emitting layeremitting red light of two sub-pixels adjacent to each other with respectto a space between the adjacent pixels along the first direction isformed as one unit, and the light emitting layer emitting blue light oftwo sub-pixels adjacent to each other with respect to a space betweenthe adjacent pixels along the first direction is formed as one unit. 3.The OLED device as claimed in claim 1, wherein the light emitting layeremitting green light of the plurality of the sub-pixels is formed as oneunit.
 4. The OLED as claimed in claim 1, wherein each of the sub-pixelsincludes an anode electrode and a cathode electrode facing each other,the light emitting layer of each of the sub-pixels being interposedbetween the anode electrode and the cathode electrode, a light emittinglayer emitting red light of the sub-pixel emitting red light beingdisposed between a light emitting layer emitting green light of thesub-pixel emitting red light and the anode electrode, and a lightemitting layer emitting blue light of the sub-pixel emitting blue lightbeing disposed between a light emitting layer emitting green light ofthe sub-pixel emitting blue light and the anode electrode.
 5. The OLEDas claimed in claim 4, wherein a hole mobility of the light emittinglayer emitting red light of the sub-pixel emitting red light is lowerthan a hole mobility of the light emitting layer emitting green light,and an electron mobility of the light emitting layer emitting greenlight is higher than an electron mobility of the light emitting layeremitting red light.
 6. The OLED as claimed in claim 4, wherein a holemobility of the light emitting layer emitting blue light of thesub-pixel emitting blue light is lower than a hole mobility of the lightemitting layer emitting green light, and an electron mobility of thelight emitting layer emitting green light is higher than an electronmobility of the light emitting layer emitting blue light.
 7. The OLED asclaimed in claim 1, wherein each of the sub-pixels includes an anodeelectrode and a cathode electrode facing each other, a light emittinglayer of each of the sub-pixels being interposed between the anodeelectrode and the cathode electrode, a light emitting layer emittinggreen light of the sub-pixel emitting red light being disposed between alight emitting layer emitting red light of the sub-pixel emitting redlight and the anode electrode, and a light emitting layer emitting greenlight of the sub-pixel emitting blue light being disposed between alight emitting layer emitting blue light of the sub-pixel emitting bluelight and the anode electrode.
 8. The OLED as claimed in claim 7,wherein an electron mobility of the light emitting layer emitting redlight of the sub-pixel emitting red light is lower than an electronmobility of the light emitting layer emitting green light, and a holemobility of the light emitting layer emitting green light is higher thana hole mobility of the light emitting layer emitting red light.
 9. TheOLED as claimed in claim 7, wherein an electron mobility of the lightemitting layer emitting blue light of the sub-pixel emitting blue lightis lower than an electron mobility of the light emitting layer emittinggreen light, and a hole mobility of the light emitting layer emittinggreen light is higher than a hole mobility of the light emitting layeremitting blue light.
 10. The OLED as claimed in claim 1, wherein thesub-pixels in a second direction emit light of a same color, the seconddirection being perpendicular to the first direction.
 11. The OLED asclaimed in claim 10, wherein each of the sub-pixels includes a firstelectrode and a second electrode facing each other, a light emittinglayer of each of the sub-pixels being between the first electrode andthe second electrode, and wherein the light emitting layer emitting redlight of two sub-pixels adjacent to each other with respect to a spacebetween the adjacent pixels along the first direction is formed as oneunit, and the light emitting layer emitting blue light of two sub-pixelsadjacent to each other with respect to a space between the adjacentpixels along the first direction is formed as one unit.
 12. The OLED asclaimed in claim 11, wherein the light emitting layers of the sub-pixelsin the second direction are formed as one unit.
 13. The OLED displaydevice as claimed in claim 1, wherein the arrangement of sub-pixelsalong the first direction with respect to color of light emitted fromrespective sub-pixels includes an order of red, green, blue, blue,green, red, red, green, blue, blue, and so forth.
 14. A method offorming an organic light emitting diode (OLED) display device,comprising: forming a plurality of pixels including sub-pixels in apredetermined order along a first direction, each sub-pixel emittingred, green, or blue light, and the predetermined order of the sub-pixelsincluding sub-pixels arranged in an order emitting red, green, and bluelights along the first direction or in a reverse order, wherein thesub-pixels formed in the pixels along the first direction are disposed,such that the arrangement of colors of light emitted from sub-pixels ofone pixel is symmetrical to an arrangement of colors of light emittedfrom sub-pixels of an adjacent pixel along the first direction, an axisof symmetry of the symmetrical arrangements being a space between theadjacent pixels, and wherein a light emitting layer of the sub-pixelemitting red light includes a light emitting layer emitting red lightand a light emitting layer emitting green light, a light emitting layerof the sub-pixel emitting the green light includes a light emittinglayer emitting green light, and a light emitting layer of the sub-pixelemitting blue light includes a light emitting layer emitting blue lightand a light emitting layer emitting green light.
 15. The method asclaimed in claim 14, wherein forming each sub-pixel includes forming thelight emitting layer between a first electrode and a second electrode,light emitting layers emitting red light or light emitting layersemitting blue light of two adjacent sub-pixels of respective pixelsadjacent to each other along the first direction being formed as oneunit via a single opening in a deposition mask.
 16. The method asclaimed in claim 15, wherein a light emitting layer emitting green lightis formed as one unit.
 17. The method as claimed in claim 15, whereinthe sub-pixels in a second direction are arranged to emit light of asame color, the second direction being perpendicular to the firstdirection.
 18. The method as claimed in claim 17, wherein the lightemitting layers of the sub-pixels in the second direction are formed asone unit.